Bamako: Islamist rebels smashed the entrance of a 15th century Timbuktu mosque on Monday, while their Al-Qaeda allies in northern Mali cut off the key city of Gao by planting landmines all around it.

In Timbuktu, the Al-Qaeda allied Islamist group Ansar Dine (Defenders of Faith) continued their destruction of the city's cultural treasures, defying a chorus of international condemnation.

Some residents sobbed as the Islamists broke down what they call the 'sacred door' of one of Timbuktu's three ancient mosques, Sidi Yahya closed for centuries due to local beliefs that to open it will bring misfortune.

In Gao meanwhile, two sources said Al-Qaeda in the Islamic Maghreb (AQIM) and its allies had planted mines around the city, with one Tuareg rebel spokesman accusing them of taking the city hostage.

Mossa Ag Attaher, spokesman for a Tuareg rebel National Movement for the Liberation of Azawad (MNLA), which until recently shared control of Gao with the Islamists, said the Islamists had "mined the area surrounding Gao".

AQIM, he said, was "using the population as hostages, as a human shield to protect itself from an MNLA counter-attack", he added.

The North African Al-Qaeda franchise and their offshoot Movement for Oneness and Jihad in West Africa (MUJAO) forced their former MNLA allies out of the city in deadly clashes last week.

"Many people are trying to escape, to take the bus to go to Bamako, but the Islamists are stopping them," said Attaher, the MNLA's Paris-based spokesman.

A west African source also confirmed that landmines had been planted around Gao "to prevent a possible attack by troops" from the west African regional bloc ECOWAS as well as a possible counter-offensive from the Tuareg fighters.

In Timbuktu, the jihadists of Ansar Dine, who occupied Mali's vast north three months ago destroyed seven tombs of ancient Muslim saints over the weekend which they consider idolatrous.